/Engine/Source/Runtime/GeometryCore/Public/Spatial/BlockedDenseGrid3.h
that provides a critical section for each block id.
template<typename CriticalSectionProviderType> void SetValueWithLock ( const [FVector3i](API\Runtime\GeometryCore\FVector3i) & CellIJK, ElemType NewValue, CriticalSectionProviderType CriticalSectionProvider )